报错信息：

Runtime Error.
Received signal 11: Segmentation fault with invalid memory reference.

代码：

#include <bits/stdc++.h>
using namespace std;
int a[10001];
unsigned long long int sum;
long int qwq(int m)
{
	return a[m]>a[m+1] ? a[m]:a[m+1] ;
}
int main()
{
	int n;
	cin >> n;
	for(int i=1;i<=n;i++) cin >> a[i];
	for(int i=1;i<=n-1;i++)
	{
		sum += qwq(i);
	}
	cout << sum;
	return 0;
}